The present invention relates to a method of transforming heat energy generated in an evaporator to mechanical energy by expanding an evaporated working fluid which is evaporated in the evaporator and expanded in the expansion device. The present invention also relates to an expansion device for transforming heat energy to mechanical energy.
A great number of methods and apparatus for transforming heat energy to mechanical energy are known from the state of the art. For example, heat engines are known, in which a working fluid is heated isobarically in a boiler under high pressures, then evaporated and subsequently super heated in a superheater. Subsequently the vapor is adiabatically expanded in a turbine where it does work and condensed in a condenser where it gives off heat. The liquid, usually water, is pressurized by a feed-water pump and recycled into the boiler. One of the drawbacks of this device is that during the expansion processes in turbines high pressures of more than 15 to 200 bar have to be generated since in turbines the pressure ratio of the expansion is essential for the efficiency to be reached. This is the main reason that in large expansion turbines the vapor is expanded into a vacuum whereby the condensation occurs at relatively low temperatures around 40° C. The condensation heat created during condensation is dissipated by means of cooling systems in a heat exchange process. This condensation heat, dissipated as waste heat, is essential in determining the efficiency to be achieved in thermal expansion processes with turbines.
Prior art transformation systems with organic solvents as working fluids (ORC systems, Organic Rankine Cycle) or the Kalina process with a mixture of water and ammonia are also based on the above vapor energy process using vaporization and condensation; they are only technical modifications so that either lower temperature or pressure levels can be used and/or to increase the efficiency by means of a better heat utilization in the boiling range.